Distribution device for automatic catalyst evaluation multi-reactors

ABSTRACT

The present invention relates to a distribution device intended for a gaseous effluent produced by a chemical reaction, comprising at least two inlet ways and two outlet ways. This device comprises at least one closed-loop line divided into four sections by four controlled sealing elements, and each one of said four ways communicates with a single section so that the inlet ways are connected to two opposite sections and said outlet ways are connected to the other two sections.

FIELD OF THE INVENTION

The present invention relates to a distribution device notably intendedfor an automatic equipment allowing multi-reactor testing of chemicalreactions, possibly in the presence of a catalyst. For this type ofequipment to work under high pressure and high temperature conditions,it necessarily comprises a distribution device withstanding theseconditions while operating a system intended for in-line analysis of thereaction products. The present invention can be advantageously automatedso that the multi-reactors can be used in parallel. Fast andsimultaneous evaluation of several sets of operating conditions thusallows acquisition of data on the progress of the reaction and on theperformances of solid catalysts.

In-line analysis is possible through precise control of the temperatureand of the total and partial pressures of the products coming from thereactors. The distribution device must also allow such control. Theelaborate automation of the assembly allows to carry out simultaneouscycles of all the reactors without the operator's intervention.

BACKGROUND OF THE INVENTION

The development of industrial refining and petrochemical processesrequires acquisition of data on the chemical reactions that take place.When these reactions are catalyzed, research and development of thecatalysts required involve evaluation of the performances thereof. Inthe laboratory, these data acquisitions and evaluations are performed inpilot plants which reproduce on a small scale the industrial operatingconditions.

There are many types of equipments allowing to measure the rate ofprogress of chemical reactions or the activity of solid catalysts. Inthe field of petroleum refining and of petrochemistry, the operatingconditions under which these measurements are performed are as follows:

pressure ranging between 1.10⁵ and 3.10⁷ Pa,

temperature ranging between ambient temperature and 800° C.,

liquid and/or gaseous reagent flow rates expressed in form of hourlyvolume flow rate per unit of volume of reactor or catalyst (hourly spacevelocity) ranging between 0.01 and 100 h⁻¹ and by the ratio of the molarflow rate of gas (most often hydrogen) and the liquid reactivehydrocarbon (H₂/HC) ranging between 0.01 and 50.

More precise selection of the operating conditions depends on the typeof process or of catalyst considered. It can be, for example, one of thefollowing industrial applications: reforming, isomerization,hydrocracking, hydrotreating, selective hydrogenation, conversion ofaromatics or oxidation.

Solid catalysts are used as balls, extrudates or powder of variablegrain size. The quantities of catalysts used in these pilot plantsgenerally range between some grams and several ten or hundred grams.These quantities are relatively great and they can be a limitation tothe use of these pilot plants. In particular, during research ordevelopment of a new catalyst, the quantities of solid catalystavailable for testing are quite often limited (less than one gram) andthere can be a great number of catalytic solid variants. All theavailable samples are therefore not necessarily tested.

The most isothermal operating conditions possible are sought for thereactors. This is generally obtained by placing the reactor in an ovenconsisting of several zones whose temperature is independentlycontrolled (U.S. Pat. No. 5,770,154). The dimensions of the reactorsalso receive particular attention. In particular, the length/diameterratio of the catalyst bed is most often selected between 50 and 200 soas to ensure proper flow of the reagents and of the products through thecatalyst, failing which diffusion or backmixing limiting phenomenadisturb measurement of the progress rates and performances of thecatalyst.

Catalysts generally require, prior to the reaction stage proper, anactivation stage which changes one or more of their constituents into areally active element for catalysis. It may be an oxide reduction inhydrogen in the case of supported metal catalysts or sulfurization inthe presence of a sulfur-containing forerunner for catalysts based onmetal sulfides. In conventional pilot plants with large dead volumes anda great thermal inertia because of the size of the ovens, thisactivation stage is generally long (typically of the order of severalhours to several ten hours).

The nature of the reagent used (most often a hydrocarbon or a mixture ofhydrocarbons) depends on the application considered. It can be a purehydrocarbon such as, for example, normal hexane, normal heptane orcyclohexane, or more or less heavy or more or less wide petroleum cutssuch as, for example, gasolines, gas oils or distillates from crude oildistillation. The quantities of reagent consumed depend of course on thesize of the reactor and on the operational time. Most often, however,the performances are calculated from inlet-outlet material balancesperformed over relatively long periods (some hours to several tenhours). These periods are necessary to allow to collect a sufficientamount (several liters to several ten liters) of products in order todraw up a precise material balance. Using a pure hydrocarbon-containingmolecule whose manufacturing cost is high is not always possible undersuch conditions.

Furthermore, during the period of evaluation of the material balance,which can be long, the catalyst may undergo a certain deactivation.Since the activity of the catalyst is not the same between the beginningand the end of the material balance, the performances calculated in fineonly reflect an average behaviour of the catalyst, far from the realevolution of the performances in time.

The effluents coming from the reactor are conventionally separated byexpansion and cooling into two phases: liquid and gaseous, whosecharacteristics and compositions are analyzed separately. These separateseparation and analysis operations inevitably lead to product losseswhich reduce the accuracy of the global material balance. In some cases,analysis of all of the products cannot be carried out at one go with asingle chromatographic analyzer. It is then possible to perform anin-line analysis before liquid/gas separation together with an analysisof the gaseous fraction taken after separation. This allows to draw upaccurate material balances in this case (U.S. Pat. No. 5,266,270).

Automation of conventional pilot plants remains quite oftenunderdeveloped. The size of these plants and observance of the safetyregulations linked with automatic operation make this automation complexand expensive. In particular, the operating conditions determining theseverity with which the reaction progresses (temperature or volume flowrate of the reagent) are most often manually adjusted by the plantoperator.

To sum up, the conventional pilot plants commonly used for measuring theprogress of chemical reactions and the performances of catalysts have acertain number of drawbacks, such as:

the necessity for a large quantity of catalyst and of reagent,

the length of the set-up time and the time required for drawing up thematerial balance required to determine the performances,

the performances reflect an average behaviour of the catalyst over arelatively long period,

the performance measurement frequency is relatively low,

complete operation automation is difficult and expensive.

On account of these drawbacks, conventional pilot plants are not verywell suited for fast and precise screening, among many catalytic solids,of the most interesting solids for development of a new catalyst orstudy of a new reaction.

SUMMARY OF THE INVENTION

The present invention thus relates to a distribution device notablyintended for a gaseous effluent produced by a chemical reaction,comprising at least two inlet ways and two outlet ways. The devicecomprises at least one closed-loop line divided into four sections byfour controlled sealing elements, each one of said ways communicateswith a single section so that the inlet ways are connected to twoopposite sections and said outlet ways are connected to the other twosections.

The device can comprise two closed-loop lines and the outlet wayscommunicate together two by two so as to form a distribution device withfour inlet ways and two outlet ways.

The sealing elements can consist of a conical needle cooperating with asealed seat.

The sealing elements can be controlled by a pneumatic jack typeoperator.

The closed-loop line can consist of four rectilinear lines arranged inthe shape of a quadrilateral, the sealing elements being substantiallylocated at the four corners of the quadrilateral.

The sealing elements can be suited for an effluent pressure andtemperature that can reach 250 b and 400° C. respectively.

The distribution device according to the invention can be applied to anequipment for performing measurements on an effluent resulting from achemical reaction taking place in a reactor containing a catalyst, andcomprising:

at least two reactors,

effluent analysis and measuring means,

means intended for automatic monitoring and control of the chemicalreaction and of the analysis and measurement cycle,

the device supplying the analysis and measuring means alternately withthe effluents from the two reactors in order to perform analysis andmeasurement cycles on two reactions progressing in parallel.

The following advantages of the device according to the invention cannotably be mentioned:

automatic measurement of the progress of chemical reactions and ofcatalytic performances in parallel in several reactors,

possible control of the partial pressures and temperatures of theeffluents in order to allow single and complete analysis withoutseparation into several fractions,

selective and frequent measurement of the reaction and catalyticperformances,

higher performance determination accuracy thanks to the limited deadvolumes,

complete progress of the operating cycles without the operator'sintervention.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will be clearfrom reading the description hereafter, given by way of non limitativeexample, with reference to the accompanying figures wherein:

FIG. 1 is the flowsheet of a testing equipment in which the deviceaccording to the invention is included,

FIG. 2 shows an example of an operational diagram of a reactor,

FIG. 3 illustrates the optimized operation of a device with fourreactors,

FIGS. 4a, 4 b, 4 c, 4 d and 4 e show the principle and an embodiment ofthe device according to the invention.

DETAILED DESCRIPTION

An example of an equipment advantageously using the distribution deviceaccording to the invention, whose flowsheet for four reaction assemblies(suffix a, b, c and d) is given in FIG. 1, consists of the followingvarious subassemblies:

a system for injecting gaseous (2 a to 2 d) and liquid (1 a to 1 d)reagents, connected to each reactor 3 a, 3 b, 3 c and 3 d,

a reaction section (3 a to 3 d) comprising several microreactors andtheir heating system,

a diluent gas pre-expansion and injection system (4 a to 4 d) at theoutlet of each reactor,

the distribution device according to the invention (5) intended fordelivery of the effluents coming from each reactor,

an analysis system (6) with in-line extraction of the sample to beanalyzed and complete expansion (7 b),

a monitoring/control unit (8) managing the assembly.

Each gaseous reagent injection system (2 a to 2 d) consists of apressure reducer-regulator, a safety valve, a pressure detector and amass flow rate regulator. The gaseous reagent is most often hydrogen.The pressure reducer-regulator allows to maintain a constant pressure atthe reactor inlet (ranging between 0 and 1.8 10⁷ Pa in relative value)from the available supply pressure. The flow rate range provided by themass flow rate regulator ranges from 5 to 500 l/h with a 1% relativeprecision. These regulators can be, for example, models 5850E marketedby BROOKS.

The liquid reagent is injected into each reactor by means of a pump (1 ato 1 d) that can be a piston type pump with a total volume of at least500 cm³ such as, for example, the 500 D pumps marketed by ISCO. Thistype of pump allows high-pressure and high-precision injection, withoutsurges, of very small quantities of liquid (ranging between 0.05 and 100cm³/h). If the viscosity at ambient temperature of the reagent is notsufficient to allow correct injection, this pump can be equipped with asystem allowing to heat it to a moderate temperature (50 to 120° C.).Similarly, the supply vessel 10 of pump 1 a (or 1 b, 1 c, 1 d) and thereagent circulation lines between supply vessel 10, the pump and thereactor must be heated for liquid reagents whose viscosity is notsufficient at ambient temperature. Mixing of the liquid and gaseousreagents is performed upstream from the reactor.

In cases where activation of the catalyst requires the presence of aparticular chemical compound, it is possible to feed the liquid reagentinjection pump from another supply vessel containing this compounddissolved in a solvent.

The inside diameter of the reactors used or microreactors ranges between0.5 and 3 cm, preferably between 1 and 2 cm for a length ranging between10 and 50 cm, preferably between 15 and 25 cm. They are arrangedvertically in an oven. The direction of flow of the reagents can beascending or descending. These reactors are made of heat-resisting steel(of Inconel 625 type for example). The cylindrical catalyst bed islocated in the central part thereof, it contains between 0.1 and 10 gcatalyst. This bed is preceded by a bed of inert material (siliconcarbide for example) having the same grain size as the catalyst, whosepurpose is to provide preheating and vaporization of the reagents. Thesereactors are axially equipped with small-diameter thermocouples (0.5 mmfor example) allowing to measure the temperature at different pointsalong the longitudinal axis. The heating oven of these reactors consistsof at least two (preferably four) zones that are independent as regardstemperature control. The first zone corresponds to the reagentpreheating and vaporization zone, the second one to the catalyst bed.The presence of various individually controlled zones guaranteesisothermal operation of the reactor along the longitudinal axis thereof.

The system (4 a to 4 d) located at the outlet of each reactor consistsof an element (11 a to 11 d) intended for pre-expansion and controlledflow rate injection of diluent gas into the various reaction productflows (hydrogen or helium for example). The pressure and the temperatureare maintained in elements (4 a to 4 d), distribution device (5) and theproduct circulation lines connecting reactors (3 a to 3 d) to analyzer(6) so that the effluent is gaseous to allow proper analysis of theconstituents. The pre-expansion overflow type element with a lowinternal volume allows to lower the pressure of the mixture of reactionproducts. Expansion to atmospheric pressure of the reaction effluents isprovided by complete expansion systems (7 a) and (7 b) respectivelylocated after distribution device (5) and analyzer (6). The distributiondevice has, in this example, as many inlets as there are reactors andtwo outlets 12 and 11, one near to the analyzer, the other near apost-expansion discharge system.

It is important to keep the reaction products in a totally gaseous statein order to allow correct analysis. In fact, the presence of liquiddroplets in the sample of these products injected into the analyzergreatly modifies the relative concentrations of the different products.The sample analyzed is then no longer representative of the mixture ofreaction products.

This is possible through control and adjustement of the temperature, thetotal pressure (by means of pre-expansion) and the partial pressures (bymeans of the dilution ratio, injection 11 a-11 d). The high-temperatureand high-pressure operating conditions of the distribution device can benoted, while inner losses and inner dead volumes likely to distortanalyses during the reaction cycle are prevented.

An example of adjustment of these parameters is described hereafter. Areactive mixture of hydrogen and paraffin hydrocarbons containing 11 to16 carbon atoms (in the proportion of 5 moles hydrogen per mole ofhydrocarbons) is converted at 380° C. and 100 bars with a rate ofconversion to lighter hydrocarbons of about 50%. At the reactor outlet,the pressure is pre-reduced to 60 bars, the temperature maintained at230° C. and diluent gas is injected at the reactor outlet. The volumeflow rate of this injection is 20 times as great as the flow rate ofhydrogen mixed with the reactive hydrocarbons at the reactor inlet.Under such conditions, the quality of the chromatographic analysis iscorrect. All the reaction products remain in the gaseous state and thesample injected into the chromatographic analyzer is representative ofthe reaction products.

The distribution device according to the invention (5) comprises aseries of valves or shutters allowing the flows coming from the reactorsto be sent to either analyzer (6) or a system (7 a) intended for directexpansion to the atmospheric pressure. At a given time of the measuringcycles, the outlet way of a reactor is communicated with line 12 of theanalyzer, the other ways being then communicated together with line 11for direct complete expansion. This distribution device 5 is illustratedin FIGS. 4a, 4 b, 4 c and 4 d.

FIG. 4a shows the principle of the distribution device, which can have2, 4, 6, . . . , 2n inlet ways and two outlet ways. The two outlet waysbear reference numbers 20 and 21. In the case shown here, i.e. with 6inlet ways, the latter are designated by A, B, C, D, E and F. Referencenumber 22 designates a line sealing element, for example a needlecooperating with a conical seat, activated by a pneumatic or hydraulicpiston type operator. The design of the present distribution inventionis based on one or more closed-loop lines (23, 24, 25). Each loop isdivided into four line sections: 23 a, 23 b, 23 c, 23 d; 24 a, 24 b, 24c, 24 d; 25 a, 25 b, 25 c, 25 d. Each section is delimited by a sealingelement 22. Each loop 23, 24 or 25 comprises two lines for two inletways A, B or C, D or E, F. These two inlet lines open each onto twoopposite sections, 23 a, 23 c; 24 a, 24 c; 25 a, 25 c. The other twosections communicate each directly with one of the two outlet ways 20,21.

Thus, if we consider the simplest case of such a distribution devicewith a single loop (two inlet ways), controlling one or the other ofsealing elements (22) delimiting an inlet line allows to selectcommunication of this inlet with one of these two outlets or the other.

If the measuring equipment comprises more than two reactors, thedistribution device comprises at least two loops whose outlet lines areconnected together, for example by lines 26, 27, as shown in FIG. 4a.

A distribution device of this type allows to use sealing elements 22,for example marketed by NOVA SWISS, which can withstand both highpressures and high temperatures, as it is the case downstream from thereactors.

Furthermore, the configuration of the lines can be such that itconstitutes a minimum dead volume, which is essential for the quality ofthe measurements and of the comparisons between the reaction cycles.

FIG. 4b shows, in side view, an embodiment of the distribution devicecomprising a housing 30 containing a block 31 wherein the effluentpassage lines have been pierced. Reference numbers 32 a, b, c and d(FIG. 4c) designate the pneumatic operators, e.g., pneumatic jackoperators, which actuate the sealing elements of the various linesections. Space 34 is filled with a thermal insulating material. FIG. 4bshows the distribution device or valve with two loops, i.e., accordingto the description above, with four inlet ways (for reactors 3 a, 3 b, 3c and 3 d) and two outlets ways. The staggered arrangement of thepneumatic operators allows to have a minimum distance between the twoplanes containing the two loops. The length of internal lines (26, 27)is thus reduced, which decreases the dead volumes.

FIG. 4c is a cross-section along plane AA (FIG. 4b). The four linesections are made by means of four non-through bores provided in block31. As shown in the enlarged view of FIG. 4E, inlet ports (35 a, b, c,d) are machined to form a sealed seat 40 so as to receive the needle 41(e.g., conical needle) of the sealing element and the joint stuffing-boxtype packings. In order to withstand average temperatures of about 250°C., the packings can be made of PEEK (polyetheretherketone). It can benoted that the sealing elements are based on the principle of leakfreeelements.

Bores 36 and 37 in block 31 are used for heating and/or regulatingelements.

Reference numbers 38 and 39 show the lines connecting the loop sectionsto the two outlets of the selection valve.

FIG. 4d is a view of section CC in the plane containing the second lineloop. The structure is identical to that of the first loop illustratedby FIG. 4c, but the sealing elements are arranged in another direction(at 90°) so that operators 33 a, b, c, d are arranged in staggered rowsin relation to operators 32 a, b, c, d.

Such a distribution device delivering a fluid under pressure (at least100 bars) and at a high temperature (at least 250° C.) is compact,readily temperature-controlled, of simplified manufacture, and readilyautomated by means of a single-acting operator. Furthermore, its designreadily allows flushing of the communication lines with a neutral gas.

The complete expansion systems (7 a) and (7 b) (FIG. 1) can be, forexample, dome overflow type models marketed by TESCOM.

Analyzer (6) allows detailed analysis of the chemical reaction products.This analyzer is equipped with a valve allowing extraction of samples ofthese products. This valve, marketed by VALCO for example, is placedunder the same temperature and pressure conditions as systems (4 a to 4d) and (5). This analyzer can be a gas phase chromatograph, i.e.equipped with one or more chromatographic columns, capillary or not,separating the reaction products by retention time difference. Thisanalyzer can be, for example, a 5890 model marketed by HEWLETT PACKARDor GC2000 marketed by THERMO QUEST.

Control system (8) manages all the various temperature, pressure, flowrate regulations, valves and actuators. This system is built around aSIEMENS automaton S7-400 and a FIX-DEMACS control software marketed byIntellution.

This control system 8 allows to carry out complete measuring cycles inparallel with the reactors. These cycles typically progress completelyautonomously in several successive stages: pressure test of theassembly, flushing with an inert gas, activation of the catalyst ifnecessary, reaction with performance measurement and finally draining ofthe installation before it is stopped. An example of a cycle is shown inFIG. 2. The progress of the cycle is shown by the evolution of thetemperature T of the reactor as a function of time H. The circuit isflushed with nitrogen from 0 to 0.5 H. The catalyst is activated byinjection at a flow rate of 1 l/h at a pressure of 90 b hydrogen from0.5 to 5 H. The reaction progresses from 5 H to 21 H with thetemperature stages shown in FIG. 2, with injection of a nC7 feedstock at1 cm³/h and hydrogen at 2 l/h. During this cycle, measuring stages M arecarried out at regular intervals.

The cycles of each reactor progress simultaneously, which allows severaltests to be carried out instead of one. An example of combination ofthese cycles is given in FIG. 3. The effluents of each reactor Ra, Rb,Rc, Rd are analyzed in turn during stages Ma, Mb, Mc, Md. It can thus benoted that, despite the duration of each test cycle, it is possible toselect one reactor after another to perform a measurement on aneffluent, which allows to carry out four tests (in the present case)practically during the same time.

EXAMPLES OF USE

1) A hydroconversion catalyst A contains Ni and Mo as the active metalphase and a zeolite of Y structure as the acid phase. Four samples (1.2g) of this catalyst are placed in the reactors of the equipmentaccording to the invention. Normal hexadecane to which 0.4% by weight ofsulfur-containing compound dimethyldisulfide and hydrogen have beenadded are used as the reagents. The operating conditions selected,identical for each reactor, are as follows:

inlet pressure: 1.5 10⁷ Pa

flow rate of reagent nC₁₆H₃₄: 0.745 g/h

flow rate of gaseous reagent H₂: 0.80 l/h

temperature: 340° C.

The reaction products are expanded to 5.0 10⁶ Pa at the reactor outlet.Dilution hydrogen is injected at a flow rate of 40 l/h at the outlet ofeach reactor and the temperature of the zones through which thesereaction products flow between the outlet of the reactors and theanalyzer is maintained at 240° C.

Prior to the reaction stage proper, an activation stage referred to ascatalyst sulfurization is carried out. This treatment consists ininjecting into the reactor the sulfur-containing compounddimethyldisulfide dissolved (1.0% by weight) in normal heptane. Theother conditions of this treatment are as follows:

inlet pressure: 6.0 10⁶ Pa

flow rate of nC₇H₁₆/C₂H₆S₂: 0.650 g/h

flow rate of gaseous reagent H₂: 0.60 l/h

temperature: 350° C.

duration: 2 h.

During the reaction stage, analyses are carried out on each reactorevery 6 hours for 180 hours, which eventually amounts to more than 120analyses. The analyzer used is a gas phase chromatograph equipped with a50-m long and 0.2-mm diameter apolar capillary column of PONA type andwith a flame ionization detector. The areas of the chromatographic peaksare used to calculate the concentrations in the various reactionproducts (normal hexadecane, isomers of normal hexadecane and lighterhydrocarbons). The conversion of normal hexadecane is calculated fromthese data.

The results obtained with all the measurements and expressed as averagevalues are as follows:

Reactor No. 1 2 3 4 Number of 28 30 27 30 analyses Average 62.1 62.361.9 62.1 % by weight conversion Standard +/− 0.7 +/− 0.6 +/− 0.6 +/−0.7 % by weight deviation

These measurements, performed in the four reactors under the sameconditions and with the same catalyst, allow to assess the globalprecision of the equipment in terms of repeatability. The relativeprecision of a conversion value provided by the equipment according tothe invention is close to 1 to 2% (ratio between the standard deviationand the average conversion).

2) Three hydroconversion catalysts B, C and D contain all Ni and Mo asthe hydrogenizing active phase and a zeolite of Y structure as the acidphase, but in different proportions in relation to catalyst A. Fastevaluation of these four samples is sought in terms of activity and ofglobal selectivity. The reagent selected therefore is normal hexadecaneto which 0.4% by weight of sulfur-containing compound dimethyldisulfideC₂H₆S₂ has been added. The four reactors of the plant are each suppliedwith 1.2 g of these catalysts. The operating conditions selected foreach reactor are as follows:

inlet pressure: 9.5 10⁶ Pa

flow rate of reagent nC₁₆H₃₄: 0.745 g/h

flow rate of gaseous reagent H₂: 0.80 l/h.

The performances are measured for four successive increasing temperaturestages 320, 340, 360 and 370° C. Each stage lasts for 2 h. A fifth andlast temperature stage is performed at 320° C. to assess the possibledeactivation of the catalysts. Analyses are carried out 1 h30 after thebeginning of each temperature stage.

The reaction stage is preceded by a sulfurization similar to the stageof example 1. The temperature, pressure and diluent gas flow adjustmentsat the outlet of the reactors are identical to those of example 1.

All these operating conditions are programmed in the automaton. Thecorresponding cycles are close to the examples shown in FIGS. 2 and 3.The total duration of a cycle is slightly less than 24 h. During thistime, there is no intervention by the operator.

The results obtained are given in the table hereafter:

Catalyst A B C D Temperature (° C.) 320 nC16 conversion 34.8 18.1 3.327.0 % by weight isomerization 24.5 17.2 4.1 12.3 % cracking 75.5 82.895.9 87.7 % 340 nC16 conversion 62.1 43.0 8.5 51.3 % by weightisomerization 43.2 37.4 10.1 20.0 % cracking 56.8 62.6 89.9 80.0 % 360nC16 conversion 90.2 62.1 20.0 75.0 % by weight isomerization 39.5 48.522.5 26.9 % cracking 60.5 51.5 77.5 73.1 % 380 nC16 conversion 98.7 84.637.4 93.2 % by weight isomerization 30.2 49.1 40.1 32.6 % cracking 69.850.9 59.9 67.4 % 320 nC16 conversion 34.5 17.9 3.2 27.0 % by weightisomerization 24.8 17.3 4.0 12.9 % cracking 75.2 82.7 96.0 87.1 %

The activity is represented by the conversion level of the reagentnormal hexadecane for a given temperature. The selectivities for thereactions of isomerization of normal hexadecane to iso hexadecane and ofcracking of normal hexadecane to lighter hydrocarbons are calculated bydividing the isomerization and cracking products yields by theconversion.

The results clearly show great differences between these catalyticsolids. Sample A is the most active whatever the temperature, whereassample C is the most selective. The relative precision obtained inexample 1 is amply sufficient to determine the differences observed.

Applied to selection of catalytic solids, the equipment and the methodusing the distribution device according to the invention thus allowfast, parallel, and high-precision evaluation of several catalyticsolids.

What is claimed is:
 1. A distribution device notably intended for agaseous effluent produced by a chemical reaction, comprising at leasttwo inlet ways and two outlet ways, characterized in that it comprisesat least one closed-loop circuit divided into four sections by fourcontrolled sealing elements, in that each one of said four wayscommunicates with a single section so that the inlet ways are connectedto two opposite sections and said outlet ways are connected to the othertwo sections.
 2. A device as claimed in claim 1, comprising twoclosed-loop lines and said outlet ways communicate together two by twoso as to form a distribution device with four inlet ways and two outletways.
 3. A device as claimed in claim 1, wherein each of said sealingelements comprises a conical needle cooperating with a sealed seat.
 4. Adevice as claimed in claim 1, wherein each of said sealing elements isactivated by a pneumatic jack operator.
 5. A device as claimed in claim1, wherein said closed-loop circuit comprises four rectilinear linesarranged in the shape of a quadrilateral, said sealing elements beingarranged substantially at the four corners of said quadrilateral.
 6. Adevice as claimed in claim 1, wherein the sealing elements are suited toan effluent pressure and temperature that reach 250 b and 400° C.respectively.
 7. Equipment intended for measurement on an effluentresulting from a chemical reaction taking place in a reactor containinga catalyst, and comprising: at least two reactors, analysis andmeasuring means intended for said effluent, means intended for automaticmonitoring and control of the chemical reaction and of the analysis andmeasurement cycle, and the distribution device as claimed in claim 1,said distribution device supplying said analysis and measuring meansalternately with the effluents from the two reactors in order to performtwo analysis and measurement cycles on two reactions progressing inparallel.